Adhesive material



Patented Jan. 28, 1930 UNITED sTATEs "PATENT OFFICE WILLIAM C. GEE R, OFAKRON, OHIO, ASSIGNOR TO THEB. F. GOODRICHOOMPANY, OF

NEW YORK, N. Y., A CORPORATION OF NEW YORK ADHESIVE MATERIAL no Drawing.

objectis to provide substances of this class having superiorcapacity forsticking to faces tough, balata-like rubberisomer, 7 parts of variouscommonly-used materials. I have found a surprisingly highsticking-quality to exist in certain artificial, tough, heat-plasticisomers of rubber, heretofore proposed for making molded goods and,electrical insulation andfor other uses not analogous to my presentdiscovery.

These isomers more or less resemble balata in some of their physicalproperties in that they are tough, fairly hard, plastic when heated,soluble in the ordinary rubber solvents, such as benzene, p-cymene,gasoline, turpentine, tetralin,-decalin, chloroform,

carbon tetrachloride, and carbon disulfide,

and good electrical insulators, but they are far superior to balata orgutta percha in surface adhesion.- They have less chemical unsaturationthan rubber, and being isomers of rubber, they contain, in a pure state,no combined oxygen and arenot allied to the resins, being substantiallyinsoluble in alcohol, ether or acetone.

Such substances may be prepared by reacting undissolved rubber, namelyrubber not in liquid solution, under the influence of heat,

with various isomerizing agents and particularly sulfonic reagentshaving the general formula R-SO X, wherein R represents an organicradical or a hydroxy group and X represents a hydroxy groupor chlorine,examples being organic sulfonyl chlorides, organic sulfonic acids andsulfuric acid or mixtures of two or more of these.

As an example of the preparation of the by weight of p-phenol sulfonicacid are mixed directly into 100 parts of undissolved rubber while beingworked on a rubber-mill, or otherwise, and when thoroughly mixed thematerial is removed from the mill and heated in a compact mass in anoven for 4 to 10 hours at i 120 to 145 C. In about two to eight hoursafter starting the heating, depending on how rapidly the batch heatsup,a pronouncedexothermal reaction sets in, the temperature in the materialrising to 200-230 C., and quantities of vapors and gases are given off.The

Application filed February 9, 1925. Seria1 No. 8,057.

heating should be continued for about two hours beyond the peak of theexothermal temperature rise.

Instead of the p-phenol sulfonic acid of the above examplev one mayemploy any of the following (a) 4 parts of concentrated sulfuric-acid(sp. gr. 1.84 (b) p-toluene sulfonic acid7 parts, a) p-phenol sulfonicacid5 parts and concentrated sulfuric acid1 part.

After removal from the oven, the product is worked or masticated on awarm mill to homogenize it, and may be washed free of remaining reagentand other water-soluble impurities during that process.

Q An alternative procedure is to form the sulfoniccompounds in therubber mass by adding to the raw rubber suitable organic compoundsandsulfuric acid and producing a reaction between the two and the rubberduring the heating of the mixture. Thus, when sulfuric acid and eitherphenol, pine tar or naphthalene are'mixed directly into the raw rubber,the sulfuric acid reacts in part with the rubber and in part with theother organic compound to form a sulfonic compound which also reactswith the rubber.

These balata-like derivatives of rubber, which constitute my adhesivematerial or the principal ingredient thereof, are found, upon analysis,to be hydrocarbons having the same carbon and hydrogen ratio as inrubber (0 11 They are however, chemically less unsaturated than rubber.They are isomers of rubber, using thatyterm in the generic sense. Theseisomers, when purified by washing, having a specific gravity of about.97 to 1.00. They are heat-plastic, softening at to 105 C. and having asomewhat indefinite melting point but not substantially higher than 2:?5 C.

The inventlon is not wholly limited to a product made with reagents ofthe class mentioned, but includes rubber isomers of the type described,no matter how produced.

The character and amount of the reagent employed and the time andconditions of cure have an important effect on the physical character ofthe product. Generally speaking, an increment in time, temperature or 10amount of the reagent used will produce harder products not quite assuitable as the softer ones. The reaction may be carried so far as toproduce hard, brittle, shellaclike products which are readily grmdableto a powder and may reglace more or less of the softer, tougher pro uctin reci es for particular uses. For instance, if t e examples abovegiven are varied by using 8 parts of p-toluene sulfonic acid, 2 partsconcentrated sulfuric acid, (sp. gr. 1.84) and 2 parts water to 100parts of rubber and heating for 8 hours at 140 C., the hard, brittleproduct results.

I find it desirable in some cases to mix about 10 per cent, more orless, of an organic flux or softener such as tung oil, castor oil, hardmineral rubber, naphthalene or Canada balsam with the balata-like rubberisomer. This improves the workability and solubility in solvents. Afurther effect of using certain of these fluxes or softeners, such astung oil castor oil or Canada balsam, in a solution of the adhesive, isto delay the dryin of the latter. An admixture of the adhesive withmineral rubber causes the compound to retain its tack for a lon er timeand also cheapens it. The use of t ese fluxes or softeners, however, isnot essential, as the rubber isomer itself possesses superior adhesiveproperties.

I also prefer to add about 1 to 5 per cent of a suitable nitrogenous,organic preservative or age-resister. Age-resistors which havesuccessfully been used are (1) the thiourea ofdimethylparaphenylenediamine, (2) 1,8 naphthylene-diamine, (3)aldol-alphanaphthylamine and (4:) benzidine.

As an example of my invention, for an adhesive of general application, Imix together on a mill, ingredients in parts by weight as follows:

Balata-like, artificial rubber isomer 86 Aldol-alphanaphthylamine 3Benzidine 1 Tung oil 10 The substitution of other softeners for a partor all of the tung oil may be desirable for particular uses. Thereplacement of part of the balata-like rubber isomer by thepreviously-mentioned hard, friable product of the same class ofreaction, and in general the addition or partial substitution ofshellac, hard resins, rubber and numerous other ingredients may beeffected when desired. The hard, friable, shellac-like isomer mayentirely re lace the tough, balata-like isomer as a su itute for shellacadhesives. Certain three-component mixtures of the tough, balata-likeand hard, rindable rubber isomers with rubber are ound to a e wellwithout the addition of any of the eforementioned age-resisters.

This adhesive may be used directly, in thin sheet form or tissue, as abond or coating, or it may be dissolved in a volatile solvent, such asbenzol, and painted on the surface or surfaces on which it is to beused. When two objects are to be connected, if it is practicable to heatthem 'and soften the cementitious material, before or while ressing theobjects together, an especially rm joint is obtained. When using theadhesive for attaching rubber to other surfaces such as metal, Isometimes employ rubber cement next to the rubber.

Various recipes using the balata-like rubber isomer as a sticking agenthave been tested and found to show remarkably strong adhesion on most ofthe common metals, wood, glass, concrete, leather, rubber, etc. Theadhesion to ferrous metal may be taken as an instance. Test samples wereprepared by sand-blasting plates of steel, painting them with a benzolsolution of the adhesive, similarly painting pieces of woven cottonfabric having a friction coating of vulcanizable rubber, and afterevaporation of the solvent, placing the coated sides together and curingin a press for 45 minutes at 145 C. After curing, the samples wereallowed to stand for 24 hours and friction pull tests were run on asuitable machine, strips ofthe fabric one inch wide being pulled. Theadhesions shown varied from 20 to pounds per inch,

.an average being about 35 pounds; Ordinary rubber cement under similarconditions gives adhesions of the order of 3 pounds per inch-guttapercha and balata 1 to 1.5 pounds and balata or gutta percha in astandard recipe with other in redients such as shellac, litharge,storax, an gum mastic with turpentine as a solvent, 2 to 3.5 pounds. Inthe same standard recipe, by substituting the balata-like rubber isomerfor the balata or gutta percha, adhesisions of 32 to 35 pounds per inchwere obtained.

Films of the tough, balata-like rubber isomer are suitable, withoutsubstantial modification of their properties, as an under-coating onsurfaces protected by ordinary paints, particularly ferrous metalsurfaces. They lend durability to the paint coating by reason of theirhigh adheslon and ability to prevent rust and corrosion.

The term rubber is employed herein in. the sense in which this term isgenerally used in the scientific. literature to indicate a caoutchoucsubstance having an empirical formula (C H and a degree of chemicalunsaturation represented by one double bond for each C H grou The termisomer of rubber is defined for the purposes of this application as asubstance derived from rubber and havin as its main constituent ahydrocarbon of t e same carbon and hydro en ratio as in rubber, namely,C,H which ydrocarbon has a less chemical unsaturation than rubber.

I claim: 1. An adhesive composition having superior surface adhesion tometal, wood, glass, concrete, leather, rubber, etc., comprising anartificial isomer of rubber having less chemical unsaturation thanrubber mixed with a relatively small proportion of a nitrogenous,organic age-resister. 2. As an adhesive, a mixture of ten h, balata-likeand hard, friable, artificial isomers of rubber.

. 3. An adhesive composition comprising a balata-like artificial isomerof rubber havlng less chemical unsaturation than rubber mixed with arelatively small proportion of a nitrogenous, organic age-resisterselected from the group which includes the thiourea ofdimethylparaphenylenediamine, ,1.8 naphthylene-diamine,aldol-alphanaphthylamme' and benzidine.

. In witness whereof I have hereunto set my hand this 6th day ofFebruary, 1925..

Y WILLIAM G. GEER.

